Tissue invasion by blood-borne malignant tumour cells and leukocytes involves their adhesion to the luminal surface of the vascular endothelium, passage through the vascular endothelial cell layer and the subsequent degradation of the underlying basal lamina and extracellular matrix (ECM) with a battery of secreted and/or cell surface protease and glycosidase activities (Nakajima et al., 1983; Schmitt et al., 1992; Vlodavsky et al., 1992).
Studies have shown that while the initial entrapment of metastatic tumour cells by the capillary endothelium is platelet-independent, platelet aggregation which occurs shortly thereafter can lead to platelet activation and degranulation, resulting in gap formation and retraction of endothelial cells, exposing the underlying basement membrane to adhesion by the tumour cells (Tanaka et al., 1986; Crissman et al., 1985; Yahalom et al., 1985).
The basal lamina and underlying connective tissue stroma consist predominantly of a complex network of fibronectin, laminin, collagen type IV and vitronectin, each of which interact with heparan sulphate (HS) side chains of heparan sulphate proteoglycans (HSPG) embedded with the matrix (Yurchenco and Schittny, 1990).
HS chains generally consist of clusters of sulphated disaccharide units (predominantly N-sulphated glucosamine linked 1-4 to .alpha.-L-iduronic acid residues) separated by lowly or non-sulphated regions (predominantly disaccharide units of N-acetylated glucosamine linked 1-4 to .beta.-D-glucuronic acid) (Turnbull and Gallagher, 1990; 1991).
In work leading up to the present invention, the inventors sought to isolate and characterise enzymes, proteins, polypeptides and peptides which are capable of cleaving the HS side chains of HSPG embedded in the matrix and genetic sequences encoding same. The genetic sequences thus derived provide a means for assisting the disassembly of the ECM and facilitating cell migration, when expressed at the matrix site or transported thereto.
The genetic sequences of the present invention further provide the means for developing a wide range of therapeutic and prophylactic pharmaceutical compounds to inhibit metastasis, neovascularisation, angiogenesis, angioplasty-induced restenosis, atherosclerotic plaque formation and inflammation and/or to promote wound healing, amongst others.